Journal of Fluid Mechanics

Papers

Interactions within the turbulent boundary layer at high Reynolds number

M. GUALAa1 c1, M. METZGERa2 and B. J. McKEONa1

a1 Graduate Aerospace Laboratories, California Institute of Technology, Pasadena, CA 91125, USA

a2 Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112, USA

Abstract

Simultaneous streamwise velocity measurements across the vertical direction obtained in the atmospheric surface layer (Reτ ≃ 5 × 105) under near thermally neutral conditions are used to outline and quantify interactions between the scales of turbulence, from the very-large-scale motions to the dissipative scales. Results from conditioned spectra, joint probability density functions and conditional averages show that the signature of very-large-scale oscillations can be found across the whole wall region and that these scales interact with the near-wall turbulence from the energy-containing eddies to the dissipative scales, most strongly in a layer close to the wall, z+ ≲ 103. The scale separation achievable in the atmospheric surface layer appears to be a key difference from the low-Reynolds-number picture, in which structures attached to the wall are known to extend through the full wall-normal extent of the boundary layer. A phenomenological picture of very-large-scale motions coexisting and interacting with structures from the hairpin paradigm is provided here for the high-Reynolds-number case. In particular, it is inferred that the hairpin-packet conceptual model may not be exhaustively representative of the whole wall region, but only of a near-wall layer of z+ = O(103), where scale interactions are mostly confined.

(Received December 08 2009)

(Revised August 25 2010)

(Accepted August 25 2010)

(Online publication January 06 2011)

Kew words:

  • atmospheric flows;
  • turbulent boundary layers;
  • turbulent flows

Correspondence:

c1 Email address for correspondence: guala@caltech.edu

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